Invasive species are one of the greatest threats to forest, range, aquatic, and urban forest ecosystem health. They contribute to the endangerment of native species and may lead to other severe ecological and financial consequences in our Nation's wild lands and urban forests. To ensure the continued production of needed goods, services, and values from our Nation's terrestrial and aquatic ecosystems, the Forest Service, an agency of the U.S. Department of Agriculture (USDA), must implement a strategic systems approach for managing invasive species. This book prioritises and guides the prevention, detection, and control of invasive insects, pathogens, plants, wildlife, and fish that threaten our Nation's terrestrial and aquatic ecosystems.